Magnetic speedometer



Dec. 27, 1938. T PAUL 2,141,445

MAGNETIC SPEEDOMETER Filed Jan. 13, 1956 flafo fai. jar/11 e11 h Jaye/Was 1455/72 63 5.

Patented Dec. 27, 1938 PATENT OFFICE MAGNETIC SPEEDODIETER Thorolf Paul,Chicago,

Ill., assignor to Stewart- Warner Corporation, Chicago, 111., a corporation of Virginia Application January 13, 1936, Serial No. 58,866

6 Claims.

This invention relates to speed-indicating and measuring instruments forvehicles, commonly termed speedometers, and its object is to provideimproved features of construction contributing to compactness of design,efficiency of operation and economy in manufacture. The invention thusconsists in such features and elements of construction as shown in thedrawing and hereinafter described, and as indicated by the claims.

In the drawing: Figure 1 may be considered a top plan view of theassembly of the internal mechanism of a speedometer embodying thisinvention.

Figure 2 is an elevation taken partly in section, as indicated at line2-2 on Figure 1.

Figure 3 is a transverse detail section taken as indicated at line 33 onFigure 2.

Figure 4 is a fragmentary side elevation to show the supporting meansfor the odometer dials.

t may be understood that, as seen in Figure l, the mechanism is viewedfrom a position opposite the plane of the dial plate but with the dialplate and outer casing omitted. The mechanism is supported in a die castframe i which, as shown, is a single casting and includes mounting meansfor the speed-indicating mechanism and for the odometer ortravel-registering ele- Sil? ments. The frame includes a journal bearing2 for the shaft 3 by which the permanent magnet l is revolved. Thisshaft includes the usual constricted portion at 5 by which the bore inits lower end is given a squared cross-section for SI intermemberingwith a suitable squared terminal of a flexible drive shaft, not shown.At its upper end, as seen in Figure 2, the shaft is reduced at 6 toengage a central aperture in a drawn sheet metal carrier cup '1 and isriveted over for permanent attachment thereto. The annular flange of thecup I fits snugly in the annular magnet 4 and its upper edge may beoffset outwardly at several points, as seen at 8 in Figure 3, forensuring a strong frictional hold.

One of these offsets, indicated at 8 engages in the gap between thepoles of the ring-shaped magnet 4. A compensating shunt member 4 ofnickel steel alloy, such as "Monel is placed in position just lappingthe poles at this gap and in contact with the ends of the magnet 4 tocompensate for temperature changes, and a pocket for this pole-piece isformed in the cylindrical wall of the cup 1 below the offset at 8*.

This magnet is made from flat strip stock bent around an axis so thatthe larger dimension of its cross-section extends parallel to the axisof the cylinder thus formed. By bending the stock from a strip in theoriginal longitudinal arrangement of its fibers is preserved from end toend. and thus from pole to pole of the magnet, improving the magneticqualities of the element as compared with one which is stamped fromsheet stock or merely cut from a block of material.

The frame I is formed with a. cylindrical cavity 10 which is concentricwith the axis of the shaft 3 and its magnet 4. A pressed metal bearingsupport in the form of a cup 9 is set into this cavity Ill with itsannular-skirt closely adjacent the magnet 4 but with ample clearance topermit the magnet to revolve freely. The lower edge of the skirt isflared outwardly in a flange H which fits snugly in the cavity I 0 andthus centers the cup 9 therein. The transverse wall of the cup isdepressed at it and carries at its center a metallic plug it into whichis set a jewel bear= ing it for the lower end of the spindle 15. Thespindle carries the non-magnetic drag element in the form of a cup l6which may he of aluminum and whose transverse web ii is fixed to atwo-part hub whose member i8 fits tight on the shaft I5 while itsapplied ring 19 cooperates with the flange of the part I8 to clamp thecentral part of the web it. A stop lug ll projects from the web it toengage with a fixed stop lug iz struck out of the web I2 of the cup 9.The skirt of the cup encircles the annular portion of the supportingelement 9 but with free running clearance so that the drag element mayrespond in the usual manner to the rotation of the magnet 3.

Just outside the aluminum cup 16 a steel field cup 20 is fittedfrictionally into the cavity 10 so as to concentrate the magnetic fiuxof the magnet 4, drawing it through the skirt and through the transversewall or web of the drag element iii. The cavity H] has a groove Ill andthe field cup 20 has a lug 2B fitting in the groove to anchor the fieldmember against rotation; and a slot 20 in the skirt of the cup 20 adaptsit to be sprung slightly and forced tightly into the socket If]. Thisadapts it to support the anchorage for the hair spring 2i which isemployed to bias the drag element 16 toward its zero position, and toyieldingly impose the magnetic drag of the magnet 4 when the latter isrevolved. The field cup 20 is apertured at the center of its web, and acollar 22 is rotatively clamped in the aperture by lugs 23 bent aroundthe rim of the aperture, as seen in Figure 2.

An outwardly extending arm 24 integral with said collar, provides ananchorage for the outer end of the hair spring 2| which is threaded intoa socket formed by oppositely offset portions 25 in the upstanding endof the arm 24 a tapered pin 26 being driven in to secure the end of thespring. A second arm 2! extending radially from the collar 22 isaccessible after the instrument has been assembled and may be providedwith an aperture 27 for conveniently engaging it by means of anysuitable tool for rotatively adjusting the collar 22 to vary the finaltension of the hair spring 2|; the frictional grip of the lugs '23 willhold the collar at any adjusted position. This provides a simple andeffective means for final calibration of the instrument.

The upper end of the spindle i is shown re-- duced at 28 and journaledin a jewel bearing 29 carried in a metallic cup 30 which is fixed in theflange 3| of a stamped cross-bar 32 which extends across the top of theframe and is secured thereto by screws 33 entering the outturned lugs 34of the frame. A suitable indicating needle 35 is provided with a hub 36which frictionally engages the reduced end 28 of the spindle |5. It willbe understood that the fiat extensions 31 of the cross-bar 32 willsupport a suitable dial plate (not shown) in a plane below that of theneedle 35 and that any suitable form of external enclosing case may beapplied, or the instrument may be mounted without any separate case backof an instrument panel board, and protected by some form of generalenclosure attached to the panel board.

The odometer train consists of several cylindrical dials 4|! adapted toregister total milage, and a lesser number of separately mounted dials4| which are intended for registering individual trips, and are adaptedto be reset to zero position at will. The resetting mechanism is offamiliar construction, including a shaft 43 having a knurled finger grip44 and carrying a gear 45 adapted to mesh with the drive gear 46 of thetrip dial series when the shaft 43 is slidably moved in its bearings forthis purpose. The conical end 41 of the shaft 43 acts as a cam againstthe rounded end 48 of the stub shaft 49 which carries the gear 45, thusshifting the latter automatically into the proper plane for meshing withthe gear 45 and disconnecting it temporarily from the gear 5|], fromwhich both sets of odometer dials are normally driven.

The dials 40 are supported loosely on a shaft 5| and the dials 4| aresupported on a shaft 52. The frame includes an upstanding web 53 havinga hole to receive the end 54 of the shaft 5|. The shaft 52 terminateswithin the elongated hub 55 of the right hand dial of the trip series.At their opposite ends the shafts 5| and 52 enter notches 56 in theupstanding web 5'! of the frame, and the reduced ends of the shafts areretained in apertures in the ends of a fiat spring member 58 secured tothe web 51 by a single fastening 59 at the middle of its length. Thisgreatly simplifies the assembly of the odometer dials in the frame, andalso permits either of them to be readily removed for repair, ifnecessary. Each train includes spacer disks 60 disposed between adjacentdials, and serving to support idler gears (not shown) which transmitmotion from one dial to the next in a familiar manner. The spacers 60are formed with bifurcated lugs 6| extending beyond the periphery of thedial cylinders and anchored against rotation by engagement with rods 62which may be removably carried in the frame webs 53 and 51 in the samemanner as the shafts 5| and 52.

I claim:

1. In a magnetic instrument, a permanent magnet composed of a piece ofbar stock completed for use by bending alone into cylindrical form witha gap between its ends, said bar having a width at least three times itsthickness and being bent so that its width comprises the length of itscylindrical form while its thickness is disposed radially thereof. meanssupporting said magnet for rotation about the axis of its cylindricalform, and a non-magnetic drag element journaled to rotate independentlyof the magnet about the same axis, and having a portion extending inclosely spaced relation to the cylindrical surface of the magnet withuniform clearance between said magnet and said portion of the dragelement throughout their relative rotational movements.

2. In a speedometer, a frame casting, a rotary magnet of annular form, ashaft fixed to the magnet, the frame casting having a journal bearingfor said shaft and a larger co-axlal recess in which the magnet rotates,a non-magnetic drag cup encompassing the magnet, a non-magnetic bearingcup disposed between the magnet and said drag cup and formed with a footflange fitted in the recess to center said bearing cup, a spindle forthe drag cup and a bearing for the spindle carried fixedly at the centerof the hearing cup, said frame casting having supporting membersextending above the bearing cup, a bar secured to said members with asecond bearing for the spindle carried by said bar, the bar having endportions offset into a plane above that of the spindle bearing forpositioning a dial plate.

3. In a speedometer, a frame casting, a rotary magnet of annular form, ashaft fixed to the magnet, the frame casting having a journal bearingfor said shaft and a larger co-axial recess in which the magnet rotates,a non-magnetic drag cup encompassing the magnet and a field member inthe form of a cup of magnetic metal fitting snugly into said recess inthe frame casting and extending over the drag cup, said cup having aslot extending through its cylindrical portion and into its transverseweb to render the cup yielding so as to be held in the recess by its ownresilience.

4. In a speedometer, a frame casting, a rotary magnet of annular form, ashaft fixed to the magnet, the frame casting having a. Journal bearingfor said shaft and a larger co-axial recess in which the magnet rotates,a non-magnetic drag cup encompassing the magnet and a field member inthe form of a cup of magnetic metal fitting snugly into said recess inthe frame casting and extending over the drag cup, said recess having aslot and said field cup having 3. lug projecting into the slot to anchorit against rotation, the field cup having a central opening in its web,a spindle for the drag cup extending through said opening, a collarfitted in the opening with portions frictionally gripping the web of thecup, a biasing spring of spiral form secured at its inner end to thespindle, an anchorage for the outer end of said spring carried by thecollar, and an arm on the collar extending radially to facilitaterotative adjustment thereof for varying the tension of the spring.

5. In a speedometer, a frame casting, a rotary magnet of annular form, ashaft fixed to the magnet, the frame casting having a journal bearingfor said shaft and a larger co-axial recess in which the magnet rotates,a non-magnetic drag cup encompassing the magnet and a field member inthe form of a cup of magnetic metal fitting tightly into said recess inthe frame casting and extending over the drag cup, the cup having acentral opening in its web, a spindle for the drag cup extending throughsaid opening, a collar fitted in the opening frictionally gripping thecup, a biasing spring of spiral form secured at its inner end to thespindle, an anchorage for the outer end of said spring carried by thecollar, and an arm on the collar extending radially to facilitaterotative adjustment thereof for varying the tension of the spring.

6. In a magnetic instrument a permanent magnet composed of a piece ofbar stock bent into cylindrical form with a gap between its ends, saidbar having a width at least three times its thickness, and being bent sothat its width comprises the length of its cylindrical form while itsthickness is disposed radially thereof, means for rotating said magnetabout the axis of its cylindrical form, and a non-magnetic drag cupjournaled for rotation independently of the magnet but disposed inco-axial relation thereto with its flange or skirt extending adjacentthe cylindrical wall of the magnet throughout the length thereof.

THOROLF PAUL.

